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Evolution of the Oman Tethyan Continental Margin |
1 Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
2 Department of Geology, The University, Leicester LE1 7RH, UK
The Oman Mountains constitute one of the best areas in which to study the development and subsequent deformation of a passive continental margin. Pulsed rifting of the Arabian craton in Early and Late Permian time was followed by Middle to Late Triassic sea-floor spreading and opening of the Tethys ocean. Passive margin subsidence continued throughout the Jurassic and Early Cretaceous, interrupted by a pulse of crustal extension in Late Jurassic (Tithonian) time. The Semail ophiolite was generated during the Cenomanian (c. 95–98 Ma), probably above a newly initiated intra-oceanic subduction zone. Mesozoic Tethyan oceanic crust was later consumed in an oceanward- (northeast-ward)-dipping subduction zone. The essential driving force was the attempted subduction of the Tethyan continental margin. Progressive collision led, in turn to the development of a peripheral bulge and foreland basin (c. 90 Ma), thrusting and eventual emplacement of the ophiolite onto the margin during late Campanian-Maastrichtian time. Thin-skinned thrust tectonics dominate the entire northern Oman continental margin, with late-stage deeper level thrusting affecting shelf edge and platform carbonates. The basal detachment extends down into deeper levels in the pre-Permian basement in the Musandam Peninsula in the north, and the Jebel Akhdar and Saih Hatat windows further south. During the Early Tertiary, continuing convergence was accommodated along the opposing Makran active margin, while a relatively stable platform was restored in the Oman Mountains area. Renewed compression during the mid-Tertiary, related to continental collision in the Zagros Mountains to the northwest resulted in short distance thrusting further onto the foreland in the northern Oman Mountains. The whole area currently lies within a zone of diachronous continental collision between the African and Eurasian plates.
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